84 DISCOVERY REPORTS 



station WS 45 between lines F and G, are shown in Table XIV, where the oxygen 

 content is shown in addition to phosphate and phytoplankton content. This line, with 

 the intermediate station, lies across the region of heavy phytoplankton production to the 

 west of the island. The correlation between the three sets of values needs no comment. 

 This area of intense production corresponds with the area of mixture of Weddell Sea 

 water and Bellingshausen Sea water, an area of warmer water, as is shown in the 

 temperature chart in Fig. 41. 



In Table XV we show the phytoplankton, phosphate and oxygen content of the 

 stations on the F line, that running to the south-west, and the intermediate station 

 WS 40 between lines F and E. Here we have at first sight the remarkable anomaly of 

 the outer stations WS 44 and WS 43 and the intermediate station WS 40 having a rich 

 phytoplankton together with a higher phosphate and lower oxygen content than the 

 inner stations WS 42 and WS 41, where the phytoplankton is exceptionally low. The 

 general water movements are shown in the phosphate chart in Fig. 39 and in greater 

 detail in Fig. 6 ; when these are referred to it will be seen that the inner stations on the 

 F line are in water which has flowed away from the scene of dense phytoplankton pro- 

 duction sampled by the G line, whereas the outer stations WS 44 and WS 43 and the 

 intermediate station WS 40 lie in the path of Weddell Sea water flowing in towards this 

 centre of rich production. This must mean that at these stations, as the water is entering 

 the region of mixture with the Bellingshausen Sea water, the intense production of 

 phytoplankton is only just beginning and has not yet had time to cause a marked 

 alteration in the phosphate and oxygen content. The water at the inner stations has 

 flowed from the scene of intense phytoplankton production, where it seems from the 

 water-movement chart that it has been eddying round for some time, giving rise to a 

 marked decrease in phosphate and increase in oxygen content ; but for some reason 

 on entering the coastal region the phytoplankton was reduced. Possibly associated 

 with the reduction in this phytoplankton, made up largely of the small Chaetoceros 

 socialis, was the presence of vast numbers of the neritic copepod Drepanopus pect hiatus 

 which were taken at these two inner stations, particularly at St. WS 42, where 2 \ millions 

 were taken in the N 70 H net just below the surface. These copepods in their millions 

 along the edge of the coastal water may have brought about a great reduction in the 

 already declining oceanic diatoms entering the area. The lack of correspondence be- 

 tween the phytoplankton production and phosphate reduction on this F line is im- 

 portant when considering the relationship of zooplankton to phytoplankton in Part V ; 

 the majority of exceptions to the working of the principle of animal exclusion there put 

 forward, where the animal plankton is correlated with phytoplankton as measured by 

 phosphate reduction, occur in the region of this line. 



It would seem, from this comparison of the phytoplankton production with the 

 phosphate reduction, together with the work of Kreps and Verjbinskaya and of Gran 

 already cited, that phosphate reduction can be used as an approximate indication of the 

 intensities of phytoplankton production in the water of an area, not, it should be pointed 

 out, immediately at the time of the phosphate sampling, but over a little time in the past. 



